Hot repair spraying material

Abstract

To provide a hot repair spraying material which has low raw material costs and can provide a high-quality sprayed object. [Solution] A hot repair spraying material containing 85 to 99.5 mass% natural magnesia clinker and 5 mass% or less (including 0 mass%) clay, characterized in that the bulk specific gravity of the natural magnesia clinker is 3.10 to 3.45 and the apparent porosity is 3.0% to 7.5%.

Description

[Technical Field]

[0001] The present invention relates to a hot repair spraying material used for hot repair of the linings of ladles, steelmaking electric furnaces, converters, and other furnaces, which is sprayed onto the surface to be repaired together with application water. In the present invention, "hot repair" refers to repair in which the temperature of the surface to be repaired is approximately 600°C or higher. [Background technology]

[0002] In various kilns, melted and damaged portions of the lining are hot repaired. As a hot repair method, for example, as shown in Patent Documents 1 to 3, a method is known in which a spraying material containing a refractory material and a binder is sprayed together with application water onto the melted and damaged portions of the lining.

[0003] Magnesia raw materials are often used as the refractory raw material for such hot repair gunning materials. Magnesia raw materials are broadly classified into natural magnesia clinker, synthetic magnesia clinker, and electrofused magnesia. Of these, electrofused magnesia has the lowest amount of impurities, so using it as the refractory raw material for hot repair gunning materials makes it easy to obtain high-quality gunning products. However, electrofused magnesia is expensive, which raises the problem of high raw material costs. In contrast, natural magnesia clinker, although inexpensive, has the problem of making it difficult to obtain high-quality gunning products. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-10642 [Patent Document 2] Japanese Patent Application Publication No. 11-130551 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-39255 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide a gunning material for hot repair which has low raw material costs and can produce a high-quality gunned product. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided the following hot repair gunning material. A hot repair spraying material containing 85 to 99.5 mass% of natural magnesia clinker and 5 mass% or less (including 0 mass%) of clay, characterized in that the bulk specific gravity of the natural magnesia clinker is 3.10 to 3.45 and the apparent porosity is 3.0% to 7.5%. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a hot repair spraying material which has low raw material costs and which can produce a high-quality sprayed product. DETAILED DESCRIPTION OF THE INVENTION

[0008] The hot repair spraying material of the present invention reduces raw material costs by using natural magnesia clinker as the magnesia raw material, and furthermore, by limiting the bulk specific gravity and apparent porosity of the natural magnesia clinker to specific ranges, and by limiting the clay content to specific ranges, it is possible to achieve a high-quality sprayed construction.

[0009] In the present invention, the bulk density of the natural magnesia clinker is 3.10 to 3.45. If the bulk density is less than 3.10, the amount of water added during spraying increases, resulting in a decrease in the density of the sprayed body. If the bulk density exceeds 3.45, rebound during spraying increases. In the present invention, the bulk density of the natural magnesia clinker is preferably 3.25 to 3.45. In the present invention, the apparent porosity of the natural magnesia clinker is 3.0% to 7.5%. If the apparent porosity is less than 3.0%, slag infiltration into the natural magnesia clinker is suppressed. However, when viewed as a whole, the difference in corrosion resistance between the natural magnesia clinker and the matrix formed of clay or the like located around the natural magnesia clinker becomes large. This promotes slag infiltration into the matrix, resulting in a decrease in the corrosion resistance of the gunned body. Furthermore, if the apparent porosity exceeds 7.5%, the number of open pores increases, which increases slag infiltration, thereby decreasing the corrosion resistance of the gunned body. In the present invention, the apparent porosity of the natural magnesia clinker is preferably 4.5 to 7.5%. Here, the bulk specific gravity and apparent porosity of the natural magnesia clinker are measured in accordance with the provisions of JIS R 2205. In the following description, natural magnesia clinker whose bulk specific gravity and apparent porosity are within the ranges of the present invention described above will be referred to as "specific natural magnesia clinker."

[0010] In the present invention, the content of the specific natural magnesia clinker is 85 to 99.5% by mass. If the content of the specific natural magnesia clinker is less than 85% by mass, sufficient corrosion resistance cannot be obtained. In the present invention, the content of the specific natural magnesia clinker is preferably 90 to 95% by mass.

[0011] In addition, in the present invention, the clay content is 5% by mass (including 0% by mass). By including clay at a content of 5% by mass or less, plasticity can be imparted to the spraying material, thereby improving adhesion. On the other hand, if the clay content exceeds 5% by mass, the viscosity of the spraying material increases, making nozzle clogging more likely to occur. In addition, the amount of water added during spraying increases, reducing adhesion.

[0012] The technical features of the present invention are as described above. The hot repair spraying compound of the present invention can appropriately contain refractory materials other than the above-mentioned specific natural magnesia clinker and clay (hereinafter referred to as "other refractory materials"), as well as a binder. The types and contents of the other refractory materials and binders are not particularly limited and may be similar to those of conventional spraying compounds. For example, various refractory materials such as alumina and silica can be used as the other refractory materials, and various binders such as phosphates, silicates, and cement can be used as the binder. The binder content can be, for example, 0.5 to 5 mass%. Furthermore, the hot repair spraying compound of the present invention can appropriately contain various additives such as dispersants, hardening adjusters, fibers, and thickeners in addition to the above-mentioned refractory materials and binders. The contents thereof may also be similar to those of conventional spraying compounds. [Example]

[0013] Table 1 shows the formulations and evaluation results of the refractory raw materials of the examples of the present invention and comparative examples. The spraying material of each example was sprayed using a conventional dry spraying machine onto the vertical surface (surface to be repaired) of a magnesia carbon brick heated to approximately 1000°C to form a sprayed body. The addition rate of water for application was 20 to 40 mass% based on 100 mass% of the spraying material.

[0014] The sprayed bodies obtained in each example were evaluated for dischargeability, adhesion, apparent porosity, and corrosion resistance in the following manner, and an overall evaluation was made based on the results of each evaluation. <Dischargeability> The dischargeability was evaluated by visually observing the nozzle tip of the dry sprayer during spray application, and a rating of ◯ (good) was given when the material was discharged without pulsation, and a rating of × (bad) when pulsation was present. <Adhesion> Adhesion was evaluated by the proportion of the sprayed material adhering to the surface to be repaired. If the proportion of the amount of sprayed material adhering to the surface to be repaired relative to the amount used was 80% by mass or more, it was rated as ◯ (good); if it was 60% by mass or more but less than 80% by mass, it was △ (fair); and if it was less than 60% by mass, it was rated × (poor). <Apparent porosity> Apparent porosity was measured in accordance with the provisions of JIS R 2205 after samples of specified dimensions cut from the sprayed body were fired at 1450°C for 3 hours. Apparent porosity after firing at 1450°C of less than 23% was rated as ◯ (good), 23% to 26% was △ (passable), and 26% or more was × (poor). <Corrosion resistance> Specimens of predetermined dimensions cut from the sprayed body were subjected to corrosion at 1650 to 1700°C for 5 hours using a rotary corrosion tester and converter furnace slag with a C / S ratio of 3.4 and a steel billet as corrosion agents. The maximum amount of corrosion loss for each example was measured and its reciprocal was calculated, and a relative value was calculated with the reciprocal of Example 1 set to 100. The larger this relative value, the better the corrosion resistance. In evaluating corrosion resistance, a relative value of 80 or more was rated as ◯ (good), a value of 70 or more but less than 80 as △ (fair), and a value less than 70 as × (poor). <Overall rating> If all the evaluation results were ◯, it was rated as ◎ (excellent); if at least one of the evaluation results was △ and there were no × evaluation results, it was rated as ○ (good); if at least one of the evaluation results was ×, it was rated × (bad); and if ◎ (excellent) or ○ (good), it was considered a pass.

[0015] [Table 1]

[0016] In Table 1, Examples 1 to 3 are examples with different contents of specific natural magnesia clinker, but all are within the range of the present invention, and good evaluation results were obtained in the evaluations of dischargeability, adhesion, apparent porosity, and corrosion resistance. In particular, Example 2, in which the content of specific natural magnesia clinker was within the above-mentioned preferred range, was given an overall evaluation of ⊚ (excellent), and a particularly good evaluation result was obtained. In contrast, Comparative Example 1 is an example in which the content of specific natural magnesia clinker was below the lower limit of the present invention, and the content of the magnesia raw material, which has excellent slag infiltration resistance, was insufficient, and therefore the evaluation of corrosion resistance was x (poor).

[0017] In Table 1, Examples 2 and 4 are examples with different clay contents, but both are within the range of the present invention, and good evaluation results were obtained in the evaluations of dischargeability, adhesion, apparent porosity, and corrosion resistance. In contrast, Comparative Example 2 is an example in which the clay content exceeds the upper limit of the present invention, and nozzle clogging occurred due to an increase in material viscosity during spray application, resulting in an evaluation of dischargeability of × (poor).

[0018] In Table 1, Examples 2, 5 to 7 are examples in which the bulk density of the natural magnesia clinker is different, but all are within the range of the present invention, and good evaluation results were obtained in the evaluations of dischargeability, adhesion, apparent porosity, and corrosion resistance. In particular, Examples 2, 6, and 7, in which the bulk density of the natural magnesia clinker is within the above-mentioned preferred range, were given an overall evaluation of ⊚ (excellent), and particularly good evaluation results were obtained. In contrast, Comparative Example 3 is an example in which the bulk density of the natural magnesia clinker is below the lower limit of the present invention, and the density of the sprayed body is reduced, so the apparent porosity is evaluated as × (poor). On the other hand, Comparative Example 4 is an example in which the bulk density of the natural magnesia clinker is above the upper limit of the present invention, and the rebound during spraying is increased, so the adhesion is evaluated as × (poor).

[0019] In Table 1, Examples 2, 8 to 10 are examples in which the apparent porosity of the natural magnesia clinker differs, but all are within the range of the present invention, and good evaluation results were obtained in the evaluations of dischargeability, adhesion, apparent porosity, and corrosion resistance. In particular, Examples 2, 9, and 10, in which the apparent porosity of the natural magnesia clinker was within the above-mentioned preferred range, were given an overall evaluation of ⊚ (excellent), and particularly good evaluation results were obtained. In contrast, Comparative Example 5 is an example in which the apparent porosity of the natural magnesia clinker was below the lower limit of the present invention. In this case, as described above, slag preferentially infiltrates into the matrix, and therefore the corrosion resistance was evaluated as × (poor). On the other hand, Comparative Example 6 is an example in which the apparent porosity of the natural magnesia clinker exceeds the upper limit of the present invention, and therefore the slag infiltration resistance is reduced, and therefore the corrosion resistance was evaluated as × (poor).

Claims

1. A hot repair spraying material containing 85 to 99.5 mass% of natural magnesia clinker and 5 mass% or less (including 0 mass%) of clay, characterized in that the bulk specific gravity of the natural magnesia clinker is 3.10 to 3.45 and the apparent porosity is 3.0% to 7.5%.

2. 2. The hot repair spraying material according to claim 1, wherein the natural magnesia clinker has a bulk specific gravity of 3.25 to 3.45 and an apparent porosity of 4.5% to 7.5%.

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